Parametrically-excited resonators



Oct. 3, 1961 o. A. JORGENSEN 3,003,068

PARAMETRICALLY-EXCITED RESONATORS Filed March 18, 1959 i v I 3\,' l I II I I I.

I N Is I L "I L J J INVENTOR.

OTTO A. JQRGENSEN WAN/5% ATTORNEY Unitem Pa fi oi PARAMETRICALLY-EXCH'EDf Otto A; Jorgensen, NY lssignor to General Dynamics Corporation, acorporation of Delaware t Filed Mar. 18,;1959,'Ser.-No;800,282 x V y 1Claim. 7 (Cl. 307-88) 7 starting signal, oscillation being sustained bychanging the impedance of the inductive tank element at a rate that istwice the resonant frequency of the tank. Such a resonator has beendescribed by Ei-ichi Goto in a paper entitled n the Application ofParametric-ally-Excited Non-linear Resonators, appearing in the Journalof Electrical Communications Engineering of June 1955. While such aresonator taken by itself may be useful, it usually finds application insystems requiring a number of intermittently operable sources orgenerators which are capable of producing synchronous signals.

Accordingly, it is an object of my invention to provide a group of newand improved signal sources capable of producing synchronous signals.

Another object of my invention is to provide a system for driving agroup of parametrically-excited resonators in synchronism.

Another object of my invention is to provide a new and improved systemfor synchronously varying the value of each of the inductive elementswithin a group of parametn'cally-excited resonators. 7

Another object of my invention is to provide a system including new andimproved paranietrically-excited resonators which continue to produceoutput signals until stopped from a common point;

I accomplish these and other objects in the preferred embodiment of myinvention which is set forth below. For the convenience of the reader,reference is made in the following'paragraphs to the drawing attached toand forming a part of the present specification which shows a schematicdiagram of a system having a group of parametrically-excited resonators.

Referring to the drawing, I provide a group of parametri'cally-excitedresonators, such as 1 and 2. While the following detailed description ofresonator operation is confined entirely to resonator 1, it is to beunderstood first, thatresonator 2 functions in the same manner, andsecond, that as many other resonators substantially identical toresonators 1 and 2 as required by the system can be provided withoutaltering the principles of operation set forth in the followingparagraphs.

Each resonator includes a tank. In the case of resonator 1, the tankcomprises capacitor 8 connected in parallel with an inductive elementwhich includes seriesconnected coils 6 and 7. Coils 6 and 7, which maybe a path concentric with core 4 are equal and opposite,

and therefore undetectable across capacitor 8. g The material anddimensions of core 4, the number of turns in coils tive for "producingsignals at substantially the resonant frequency of the tanks. Meansindividual to each resonator, such as normally open, manually operableswitch 9 in thecase of resonator 1,-is provided for connecting generator10 across the corresponding tank, so that gene erator 10 momentarilydrives resonator l at its resonant 7 frequency from the time switch 9contacts are closed 'until they are reopened. The effect of 'thismomentary starting signal tothe' tank of any resonator is'to beexplained presently.

The material used to form core 4 is chosen so that the permeability, andhencethe inductance of coils 6 and 7, changes as the magnetic fluxdensity within core 4 is changed. This non-linear characteristic of theinductive element of each tank is used to sustain resonator 1 and i allother resonators in oscillating condition after a starting signalhas'been applied to their tanks. Accordingly, I provide a second signalsource including generator 11 which is common to all resonators and iscontinuously operative for producing a signal at substantially twice theresonant frequency of the tanks within the various resonators. In orderto modify the inductance presented by the inductive element within thetank of each resonator,

winding 14, which embraces core 4, is operative in response to thecurrent flow therein for exciting core 4, i.e., controlling the fluxdensity in and concentric with core 4, thereby controlling thepermeability of core 4. Means including battery 12, variable resistor13, and normally closed switch 15 is provided for connecting generator11 in series with coil 14. With this arrangement, the flux densitywithin core 4, and hence the induction of coils 6 and 7, is varied attwice the resonant frequency of the tanks within the various resonators.By adjusting the value of resistor l3, the flow of direct current frombattery 12 through coil 14 is regulated to drive the average fluxdensity within core 4 to the point where the permeability of core 4swings within the upper and lower limits as the alternating currentcomponent from generator 11 is passed through winding 14 requiredtochange the inductance presented by the coils within the variousresonator tanks sufficiently to sustain oscillation within thoseresonator tanks.

In the absence of an exciting signal from external generator' 10, noneof the resonators including 1 produces a signal across its tank eventhough current fromgenerator 11 continues to flow through winding 14.However, the operation and release of switch 9 in theaforernentionedmanner and the resulting momentary application This continuing signalacross the tank constitutes an output signal for the resonator and, assuch, is coupled directly to load 5, where it is utilized. 7

In order to stop all resonators at the same time, normally closed switch15 is operated and thereby stops the previously described change ofpermeability within core 4. As a result, the value of the inductiveelement within the coils of all resonator tanks becemesfixed. and themimetic, 3, 1951 signal across the outputs'of the actuated ones of theresonators decaystozero. Switch 15 can thereuponbe-rement of myinvention, other modifications will readily occur to those skilled inthe art.

I do not therefore desire my invention to be limited to the specificarrangement shown and described andI intend in the appended claim tocover all such modifications within the true spirit and scope of myinvention.

What I claim is:

In a'signaling system, a plurality of substantially identicalparametrically-excited resonators, each of said resonators comprisingfirst and second windings and a capacitor, a multi-aperture core ofmagnetic material common to said resonators, said core having anaperture for each of said resonators, said first and second windings ineach resonator being wound through the aperture for that resonator andaround an individual portion of said -4 a core, means for connecting thefirst and second windings in each-resonator in seriesopposition andin'circuit with the capacitor in that resonator to form a resonantcircuit having a resonant frequency f, a control winding disposed ininductive relationship with said core, means for applyingan-excitingsignal having afrequency which is a harmonicoffrequency f to saidcontrol winding, and means for' selectively applying an input signal offrequency f-to tlieresonant circuit in any one of said resonators.

References Cited in the file of this patent UNITED STATES PATENTS1,544,381 *Elmenet a1. June 30, 1925 15 FOREIGN PATENTS 778,883 GreatBritain July 10, 1957 OTHER REFERENCES Magnistor, published by PotterInstrument Co., Inc., 20 11s Cutter Mill Road, Great Neck, NY. 4 pages).

